In a semiconductor manufacturing process, the evaporation technology is often required. Taking the preparation of an organic light-emitting diode (OLED) display screen as an example, it is required to use a fine metal mask (FMM) and heat material to be evaporated from below, so that the material is evaporated or sublimated upward and then deposited or sputtered onto the surface of a substrate to be evaporated by passing through a designed opening of the mask, to form a desired film pattern.
FIG. 1 and FIG. 2 are schematic structure diagrams of an existing mask plate for evaporation. The mask plate generally includes a frame 11, a plurality of masks 12, a shielding film 13 and the like. The plurality of masks 12 and the shielding film 13 are all welded onto the frame 11 provided for carrying them thereon. The plurality of masks 12 are required to be combined with the frame 11, i.e., to be stretched. The shielding film 13 is required to be welded in a gap 14 between adjacent ones of the masks 12 to shield the gap 14, to prevent the material from being evaporated onto the substrate by passing through the gap 14 to result in color mixture.
During stretching, the shielding film 13 is welded onto the frame 11 first, and then the masks 12 are welded. A recessed portion for placing the masks 12 and the shielding film 13 therein will be provided on the frame 11 in advance. In order to ensure the flatness of the entire mask plate, a groove, reversed for the shielding film 13 on the frame 11, will be provided on the bottom surface of the recessed portion reserved for the masks 12, as shown in FIG. 2.
Generally, the masks 12 are very thin. In the prior art shown in FIG. 2, as arranging the groove reserved for the shielding film 13 on the bottom surface of the recessed portion reserved for the masks 1.2 breaks the bottom surface of the recessed portion reserved for the masks 12 and thus this bottom surface is not continuous, edges and corners, closer to the gaps 14, of the masks 12 are not supported by the frame 11 and also not welded onto the frame 11. This easily results in warps, crimps and other undesirable phenomena of the masks 12 at these positions. Furthermore, when welding the masks 12, it is required to apply a tension to the masks 12 to flatten the masks 12, and at the same time, the welding is performed by using welding tools. If the tension is not appropriate during welding, the masks 12 will be folded, thereby reducing the evaporation yield.